The present invention relates generally to a keyless entry system for operating automotive vehicle devices such as door locks, a trunk lid lock, a glove box lid lock, a steering column lock and/or a starter motor, without using any mechanical keys, such as ignition key. More specifically, the invention relates to a keyless entry system which includes a compact, pocket-portable wireless code transmitter of a size comparable to a creditcard, and a feature for preventing the transmitter from being locked in the vehicle.
Conventionally, automotive door locks, trunk lid locks, glove box lid locks, steering lock devices and so forth have been operated by means of ignition or other mechanical keys. Recently, so-called "Keyless Entry Systems", which do not require keys to operate door locks, trunk locks, vehicle window regulators and so forth, have been developed. In such keyless entry systems, a keyboard is provided on the external surface of the vehicle body to allow entry of a preset code authorizing access to one of more desired vehicle devices. The designated vehicle devices are electrically operated when the entered code matches a preset code.
U.S. Pat. No. 4,205,325, to Haygood et al, discloses a keyless entry system for an automotive vehicle permitting a plurality of operations to be achieved from outside of the vehicle by one who is knowledgeable of preset digital codes. Functions such as unlocking the vehicle doors, opening the trunk lid, opening windows, operating the sun-roof or programming the system with a user-preferred digital access code can all be performed by proper sequential operation of a digital keyboard mounted on the outside of the vehicle.
This and other conventional keyless entry systems require the user to accurately input the preset code through the keyboard. Although such keyless entry systems have been well developed and considered useful for eliminating the need for mechanical keys, a serious problem may occur when the user of the vehicle forgets the preset code. If the user is outside of the vehicle and the vehicle door lock device is holding the door locked, the user cannot unlock the door lock until he remembers the preset code.
In order to resolve this defect in the prior art and allow convenient use of the keyless entry system, there has been proposed a new approach in which a pocketportable wireless transmitter, of a size comparable to a creditcard and thus capable of being carried in clothing pockets, is used to identify users authorized to operate vehicle devices. This new keyless entry system has been disclosed in the Published Japanese Patent Application (Tokkai) Showa No. 59-24075, published on Feb. 7, 1984, (Japanese patent application No. 57-132118, filed on July 30, 1972). In the disclosed system, door locks, a trunk lid lock and so forth can be operated with a single push-button action. The wireless transmitter always becomes active in response to operation or depression of any one of the push buttons to operate a desired vehicle device. This means that whoever possesses the transmitter has full access to the vehicle and that whenever the transmitter is near enough to the vehicle, keyless entry is possible for any one at all. As a result, if the user should lock the transmitter in the vehicle and leave the vehicle, anyone would be able to unlock the door, turn on the starter motor and steal the vehicle. In addition, it would be highly likely for items stored in the trunk and/or glove box to be stolen when the transmitter is left in the vehicle.
In the prior system, we still require at least one stroke of a push button operation for operating each vehicle device. For instance, each one stroke of a push button operation is required for performing door locking, unlocking, steering locking or unlocking and so forth. To the contrary, the conventional mechanical key system allows automatic lock of steering by releasing the ignition key from the key cylinder.